Exhaust Manifold Bolts

[ike84]

Originally Posted by husker boxster

I'm hoping to change out the driver's side exhaust manifold today (bad cat). When removing the exhaust manifold bolts going into the engine block, should I...

1) Give 'em the beans and hit them with an impact wrench

or

2) Carefully hand loosen them

I'm really afraid of breaking them off so I'm wondering if either of these approaches is better. I'm leaning towards #1. I've been squirting them with AeroKroil several times over the last 24 hrs in preparation of the extraction.

Please, for the love of all that is holy, do not use an impact on these.

I agree that repeat oiling and whacking over several days is the best first step.

I watched an interesting video a mechanic made about removing seized header bolts. He would actually tighten them until you could feel the cracking of the rust, then loosen quarter of a turn, then tighten again, then loosen again, etc. Take your time, don't force it, and don't actually remove any of the bolts until they are all cracked free. Start with the front and rear ones first as they are usually the hardest ones (and will only get more difficult if you save them for last). This was the technique I used in mine and 11/12 came out fine. The integrity of the metal on the rear most bolt on driver's side was so poor that I could actually feel it twisting but not breaking free. That one had to be drilled out.

Do yourself a favor - when you replace them, don't use standard hardware. Go with SS studs (tightened with hex key for your toque wrench) followed by copper plated nuts. Using dissimilar metals will reduce the risk of contact welding as corrosion and heat cycles do their damage.

Let me know if you need part numbers for the studs and bolts. There are "porsche specific" kits that will run you well over $100 but I bought universal parts for $25 and they worked just fine.

Btw, when I dismantled mine, I found that the top not on the triangular flange between header and midpipe were spot-welded by the factory. I'm not the only one to have found this, but it doesn't seem to be universal though.

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[elgyqc]

Originally Posted by ike84

... Do yourself a favor - when you replace them, don't use standard hardware. Go with SS studs (tightened with hex key for your toque wrench) followed by copper plated nuts. Using dissimilar metals will reduce the risk of contact welding as corrosion and heat cycles do their damage.

Let me know if you need part numbers for the studs and bolts...

I just finished drilling out 3 broken bolts and installing helicoils on the spare engine I bought. So would appreciate the part numbers you mentioned.

[ike84]

Originally Posted by elgyqc

I just finished drilling out 3 broken bolts and installing helicoils on the spare engine I bought. So would appreciate the part numbers you mentioned.

M8 x1. 25 x 50mm studs. I got mine on Amazon but they're currently out of stock, but are oem for ford 4.6 and 5.4 L V8s. You could get by with a 45 mm length if you can find it but the 50s are fine. The ones I found were fully threaded but a lot are only threaded in each with a blank in the middle where the header sits. The block depth is 24mm, so just keep that in mind if you go with that type. Also, not all of them have the slot for the hex head. This is important since they should be torqued to spec. The nuts are just m8*1.25 13mm copper plated flange nuts, again procured on amazon I'm sure that I shouldn't have, but I used antisieze on the threads.

I've never heard of helicoils before! Do they really work? I stripped out one of my rear sway bar bolt holes recently and there wasn't enough left to retap, so I've got a longer bolt with a nut on it for now. The OCD in me would love to try make it all match again though lol.



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[elgyqc]

Originally Posted by ike84

... I've never heard of helicoils before! Do they really work? I stripped out one of my rear sway bar bolt holes recently and there wasn't enough left to retap, so I've got a longer bolt with a nut on it for now. The OCD in me would love to try make it all match again though lol...

Thanks for the info on the studs.
Yes helicoils work, I have used them a couple of times before. My engine won't be installed for awhile so I have not yet installed and torqued the header bolts. I bought a kit on Amazon with several sizes of helicoils including the proper drill bits and tools needed for the installation.